1. Field of the Invention
This invention relates to the field of roll sensors for vehicles. More particularly, the present inventions relate to the use of angular rate to determine a vehicle roll condition and to the use of angular rate sensors and incline sensors to accurately indicate that a land vehicle roll condition has occurred.
2. Description of the Prior Art
In the past it has been known to use accelerometers for detecting vehicle roll conditions. However, under certain conditions it would be desirable to use an angular rate sensor, alone or in combination with an incline sensor, to accurately anticipate a roll condition and to activate a safety system before the vehicle rolls over.
In the past, gyros have been used in land vehicles for the purpose of aiding in navigation. In these systems it has been found that over time, the output of the gyro drifts due to temperature and other factors. Extremely precise gyros which minimize drift are available, but can be very expensive. There have been patents in the past that have used gyros for navigation control of a vehicle, and which have established systems for compensating for the bias or drift in the gyro output. For example, U.S. Pat. No. 5,270,969 to Matsuzaki et al., entitled BIAS CORRECTION APPARATUS OF GYRO, discloses the use of a gyro, among other elements, in a vehicle navigation system, where the gyro output bias is corrected using a bias stored in the buffer memory during the time the vehicle is at a stop. Additionally, U.S. Pat. No. 4,321,678 to Krogmann uses a gyro to determine the position of a vehicle. In that patent an estimated value of the gyro drift is obtained in a filter by comparison with a magnetic heading and is taken into account.
There is a need for a land vehicle roll sensor system that can collect data and use logic to discern between roll and non roll conditions and provide for an accurate determination that a safety system trigger event has occurred.
These objects, and others, are satisfied by Applicant""s present inventions disclosed herebelow.
One embodiment of the present inventions relates to the use of both angular rate and an angular rate derived angle to determine whether a vehicle safety system trigger event has occurred.
Other embodiments of the present inventions relate to the use of an angular rate sensor in a roll sensor system for a land vehicle to anticipate vehicle roll and to activate a vehicle safety system under roll conditions. In that embodiment, drift in the angular rate sensor output is compensated for periodically, including while the vehicle is in motion.
In other embodiments of the present inventions, a roll sensor system uses both an incline sensor and an angular rate sensor to accurately predict and detect vehicle roll conditions.
In other embodiments of the present inventions, to insure accuracy an incline sensor output and/or a signal derived from the incline sensor output is compared to a value obtained from and/or derived from an angular rate sensor output, to determine if the incline sensor output is valid. If valid, the incline sensor output is referenced in order to determine whether to trigger a vehicle safety system.
Related objects and advantages of the present invention will be apparent from the following description.